12 February 2018

The gut microbiota

gut bug

By Daniel So - Research Dietitian and PhD Candidate

What is the gut microbiota?

The human microbiota is made up of the trillions upon trillions of microorganisms residing in and on the body. These bugs are spread out throughout the body and congregate at specific sites, including the mouth and lungs, and often live in harmony with the human host. The majority of these microbes are found along the gastrointestinal (GI) tract, which offers approximately half a badminton court’s worth of space for these bugs to occupy (1).

What’s so exciting about it?

Advances in technology over the past 10 years have allowed researchers to characterise and better understand these bugs. We now know that approximately 160 different species of bacteria call the GI tract home and together, possess over 100 times more genes than the human genome (2). This allows these gut bugs to do many things that our bodies cannot – such as breaking down undigested food and offering protection against certain pathogens (2, 3). So much so, that our gut microbiota starting to be referred to as an extra organ!

What does it mean for me?

As we discover and understand more about the gut microbiota, it is becoming increasingly apparent that these gut bugs aren’t simply along for the ride. Rather, they serve an important role in maintaining our health and wellbeing. Recent studies have linked a large number of disease states with dysfunctions of the gut microbiota (4, 5) – whether it’s a decrease in the number of bacterial species or aberrations to specific types of bacteria. As a result, these gut bugs may be key players in the development and management of these conditions!

The gut microbiota is also affected by a number of other factors, such as antibiotic use, diet and your environment (2, 5). The good news is that diet – something that we can control – has a major impact on these gut bugs, from supporting the growth certain types of good bugs and maintaining its microbial diversity!

What’s next?

Over the next few weeks, we will go down the rabbit hole and explore these gut bugs in more detail, covering topics including what types of bugs make up the gut microbiota, their role in IBS, and how diet can keep them happy.

Thanks to these bugs, we are always surrounded by trillions of friends!


1.    Helander HF, Fandriks L. Surface area of the digestive tract - revisited. Scandinavian journal of gastroenterology 2014;49(6):681-9. doi: 10.3109/00365521.2014.898326.

2.    Marchesi JR, Adams DH, Fava F, Hermes GD, Hirschfield GM, Hold G, Quraishi MN, Kinross J, Smidt H, Tuohy KM, et al. The gut microbiota and host health: a new clinical frontier. Gut 2016;65(2):330-9. doi: 10.1136/gutjnl-2015-309990.

3.    Sekirov I, Russell SL, Antunes LC, Finlay BB. Gut microbiota in health and disease. Physiological reviews 2010;90(3):859-904. doi: 10.1152/physrev.00045.2009.

4.    Zhernakova A, Kurilshikov A, Bonder MJ, Tigchelaar EF, Schirmer M, Vatanen T, Mujagic Z, Vila AV, Falony G, Vieira-Silva S, et al. Population-based metagenomics analysis reveals markers for gut microbiome composition and diversity. Science (New York, NY) 2016;352(6285):565-9. doi: 10.1126/science.aad3369.

5.    Lozupone CA, Stombaugh JI, Gordon JI, Jansson JK, Knight R. Diversity, stability and resilience of the human gut microbiota. Nature 2012;489(7415):220-30. doi: 10.1038/nature11550.

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